Chain saw



F. T. IRGENS Jan. 2, 1968 CHAIN SAW Filed Nov. 12, 1963 INVENTOR. //wv Z /E-En/5 Arroewsv! United States Patent Ofiice 3,361,165 Patented Jan. 2, 1968 3,361,165 CHAIN SAW Finn T. Irgens, Milwaukee, Wis., assignor to Outboard Marine Corporation, Waukegan, Ill., a corporation of Delaware Filed Nov. 12, 1963, SB!- No. 323,011 11 Claims. (Cl. 143*32) The invention relates generally to engine driven devices such as chain saws.

The invention generally involves, in part, the provision in a chain saw of a safety clutch to prevent operation of the chain saw when it is not properly held. The invention also involves provision for preventing throttle advancement of the engine beyond a predetermined low setting prior to driving engagement of the safety clutch. More specifically, in a preferred embodiment, the forward handle bar of a chain saw is provided with a hand grip or lever which is operable through a flexible cable, to withdraw a remotely located plunger from a biased, interfering position in the path of a part of a helical clutch spring connecting a pair of driving and driven members. Rotation of the clutch spring aid driving engagement of the members is thereby permitted. Also provided is a button control for holding the hand lever in the position which withdraws the plunger.

Control of the throttle is provided by connecting the hand grip by means of a flexible cable with a stop member which is movable relative to a position preventing throttle advancing movement of a throttle controlling trigger. Thus, when the hand lever is not gripped and thereby closed, driving engagement of the clutch members is prevented as well as throttle advancement above a predetermined level. However, when the hand grip is depressed, the plunger is withdrawn from interfering engagement with the clutch spring and the interference to movement of the throttle controlling trigger is removed. In the event the grip on the hand lever is loosened, the clutch will be disengaged and the travel of the saw chain will stop.

Other objects and advantages of the invention will become known by reference to the following description and accompanying drawings in which:

FIGURE 1 is a fragmentary perspective view of a chain saw embodying various of the features of the invention;

FIGURE 2 is an enlarged fragmentary view of the engine crankshaft and clutch mounted thereon;

FIGURE 3 is a fragmentary view illustrating the hand grip or lever mounted on the forward handle bar;

FIGURE 4 is a sectional view taken along line 44 of FIGURE 3;

FIGURE 5 is an enlarged fragmentary view, partially broken away, illustrating the mounting of the throttle controlling trigger and connected linkage; and

FIGURE 6 is a fragmentary view taken at a right angle to the view shown in FIGURE 5.

The chain saw 11 shown in the drawings includes a frame 13 including a forward handle bar 15 and a rearward handle 17. Carried by the frame 13 is an engine 19 including a crankshaft or output shaft 21, together with a centrifugal clutch 23 connecting the crankshaft 21 to a chain sprocket 25. Trained around the chain sprocket 25 and guided by a cutter bar 27 supported by the frame 13 is a saw chain 29. Forming a part of the engine 19 is a carburetor (not shown) which includes a throttle (not shown) controlled by a linkage 35 (see FIGURE 5) connected to a throttle controlling trigger 37 pivotally mounted on the rear handle 17. The above components are all generally Well known.

In order to afford stoppage of the travel of the saw chain 29 in the event the chain saw 11 is no longer properly held by the operator, the chain saw includes a safety clutch 39 interposed between the crankshaft 21 and the sprocket 25, together with means normally preventing driving engagement of the crankshaft 21 and the sprocket 25 by the safety clutch 39, and manually operable means for overriding said means normally preventing driving engagement between the crankshaft and the sprocket.

In the illustrated preferred embodiment, the safety clutch 39 is embodied as a part of the structure of the centrifugal clutch 23. More specifically, the centrifugal clutch 23 includes two or more clutch shoes or flyweights 41 which are keyed to the crankshaft 21 for rotation therewith and which, in response to such rotation, swing outwardly to engage the inner surface of a first drum 43. This drum, in addition to acting as one component of the centrifugal clutch, also serves as the driving member of the safety clutch 39. The drum 43 is carried for free rotation about the axis of the crankshaft 21 on a hub 45 which is rotatably mounted on the crankshaft 21. Also carried on the hub 45 for rotation therewith is the chain saw sprocket 25 and a second drum 47 which constitutes the driven member of the safety clutch 39. The drums 43 and 47 are therefore mounted for co-axial rotation, each respectively including an outer cylindrical surface 49 and 51, which surfaces are located in axially adjacent registry with each other.

The drum 47 is driven by the drum 43 in response to rotation of the latter by a helical clutch spring 53 which has one end fastened to the driven drum 47 and which closely encircles both cylindrical surfaces 49 and 51. The helix of the spring 53 is arranged so that rotation of the drum 43, and the resultant frictional contact between this drum and the spring, causes the spring 53 to be wound tightly around both drums to effect driving engagement by the drums 43 and 47 and resultant travel of the saw chain. The spring 53 is enclosed in a cover 55 mounted on the drum 47.

Driving engagement between the drums 43 and 47 is prevented, except when the chain saw is properly held, by manually controllable means for controlling the engagement of said chain sprocket 25 and said shaft 21 by said clutch 39. Such means includes a part 57 extending radially from the helical clutch spring 53, which part 57 extends through an opening in the cover 55, and a plunger 59 which is mounted on the frame 13 and is biased by a spring 61 to a position interfering with rotation of the helical spring part 57. Thus, when the plunger is in its interfering position, rotation of the spring is prevented, thereby precluding winding up of the clutch spring upon the drums to initially drivingly engage the safety clutch or to cause release of the tight engagement of the clutch spring with the drums after previous driving engagement so as to effect stoppage of further saw chain travel.

Withdrawal of the plunger 59 from its interfering position to permit driving of the chain saw through the safety clutch 39 is provided by means for manually overriding the action of the plunger biasing spring 61. Such means includes a flexible cable 63 connected to the plunger 59 and to a hand grip, or trigger, or lever 65 pivotally mounted on the front handle bar 15 in position for gripping by the operator.

More particularly, adjacent one end 67, the lever 65 is rockably mounted about a pivot 68 which is located in spaced relation to the handle bar 15 on a yoke 69 suitably secured to the handle bar 15 as by the screws 71. Fixed between the lever 65 and the handle bar 15 is a spring which biases the handle end 73 of the lever 65 away from the handle bar 15 and to its safety position which permits displacement of the plunger 59 into interfering position with respect to the clutch spring part 57.

The flexible cable 63 is anchored by suitable means to a lug 77 which projects from the lever 65 so as to longitudinally displace the cable 63 in response to lever movement. Preferably, the cable 63 is covered by a sheath '7? which, at one end, is anchored to a projecting part 31 of the yoke 69 and, at its other end, is anchored to a nipple 83 secured to the frame 13 in enclosing relation to the plunger biasing spring 61.

The action of the lever biasing spring 75 in restoring the lever 65 to its safety position can be overcome to facilitate engine operation during warm-up periods and the like, when the chain saw is not actually in use, by detent means comprising a spring loaded button 85 carried by the yoke as and movable into a position holding the lever 65 with the handle end 7'3 in a substantially depressed position in close proximity to the handle bar 15. More particularly, the button 85 includes a head 87 which is movable in a bore 89 in the yoke 69 and a stem 91 which extends from the head 87 and passes through an aperture 93 of reduced size at the inner end of the bore 89. Located between the head 87 and the inner end of the bore 89, in encircling relation to the stern 91, is a spring 95 which serves to bias the button 85 outwardly of the yoke 69.

At the other end of the stem 91 is an enlarged part 97 which limits outward movement of the button and which is movable against the action of the spring 95 into a position between the lever end 67 and the handle bar id to prevent movement of the handle end of the lever from a substantially depressed position. Action of the lever biasing spring 75 prevents withdrawal of the button 85 from between the lever 5 and the handle bar 15 in the absence of movement of the handle end 73 of the lever toward the handle bar 13 by the operator. Thus, the lever can be retained in a substantially depressed position etfecting withdrawal of the plunger 59 by squeezing the lever to its fully depressed position and by then positioning and retaining the button inwardly of the yoke during subsequent release of the lever from its fully depressed position. The detent is releasable merely by subsequently squeezing the lever to its fully depressed position and permitting withdrawal of the button 35.

Also incorporated in the chain saw 11 is throttle interlock means for preventing advancement of the engine throttle when engagement of the safety clutch 39 is prevented by location of the plunger 59 in its position interfering with rotation of the clutch spring 53. As already ientioned, the engine throttle is controlled by the trigger 37 which is rockably mounted on a pivot 99 in the rear handle 17. Connecting the trigger 37 with the throttle is the linkage 35 which is pivotally connected, at 101, to the throttle trigger 37 on one side of the pivot Q9. The means for preventing advancement of the throttle comprises a portion H33 of the trigger 37 extending on the other side of the pivot pin 99, together with a throttle stop 105 which is mounted in the rear handle 17 for pivotal movement about a pin 107 relative to a position interfering with the trigger portion 103 to prevent advancement of the throttle above a predetermined level. Connected to the throttle stop 1G5 is a flexible cable 109 which is anchored at its other end in tne lug 77 of the lever 65. The connection of the cable Th9 with the throttle stop W is such as to locate the throttle stop in its interfering position when the lever 65 is in its safety position permitting disposition of the plunger 59 in position to prevent engagement of the safety clutch 39. When the lever 65 is moved to its depressed position permitting engagement of the safety clutch 39, the cable MP9 rocks the throttle stop 195 from its interfering position, thereby permitting full control of the throttle by the trigger 37. Preferably, the cable is enclosed in a flexible sheath ill which is anchored, at one end, to a projecting part 31 of the yoke 69 and, at its other end, to a clip 1513 fixed to the rear handle 17.

Although the safety clutch and throttle interlock features of the invention have been described above in connection with a so-called direct drive chain saw, i.e., a chain saw without a speed reducing gear drive, it is obvious that the principles of the disclosed invention are also applicable to chain saws including gearing for reducing the rotational speed of the saw chain sprocket as compared to that of the crankshaft. In addition, the safety clutch feature of the disclosed invention is also equally applicable to chain saws driven by electric motors. The throttle interlock feature is also applicable to such electric motor driven chain saws which include speed controlling means. While various of the features of the invention find particular utility in chain saws, various of the features of the invention are also usable in connection with other engine powered devices, such as lawn mowers.

Various of the features of the invention are set forth in the following claims.

What is claimed is:

1. The combination in a chain saw of an engine having an output shaft, a handle connected to said engine, a chain sprocket adapted for driving a saw chain, a cutter bar extending from said sprocket, a clutch releasably connecting said sprocket and said shaft, said clutch including a driving member, a driven member, and means for engaging said driving and driven members in driving relationship, means associated with said means for engaging said driving and driven members and normally preventing engagement of said means for engaging said driving and driven members, and manually operable means on said handle for overriding said means normally preventing engagement of said means for engaging said driving and driven members.

2, The combination in a chain saw of an engine having an output shaft, a handle connected to said engine, a chain sprocket adapted for driving a saw chain, a cutter bar extending from said sprocket, a clutch releasably connecting said sprocket and said shaft and including a driving member comprising a first, rotatably mounted drum, a driven member comprising a second drum rotatably mounted co-axial with said first drum, said first and second drums including aligned cylindrical surfaces, and means for engaging said driving and driven members in driving relationship comprising a helical spring encircling said cylindrical surfaces to provide driving engagement therebetween in response to rotation of said first drum, means associated with said means for engaging said driving and driven members for normally preventing engagement of said driving and driven members and comprising a radially extending part on said helical spring, a plunger movable into a position in the path of rotative movement of said spring part to prevent rotation thereof and thereby to prevent driving engagement of said drums, means biasing manually operable means on said handle for plunger toward said position, and said overriding said means normally preventing engagement of said driving and driven members and including a trigger pivotally mounted on said handle, means connecting said trigger and said plunger to effect displacement of said plunger from said position in response to pivotal movement of said trigger, and means biasing said trigger to a position permitting movement of said plunger to its said position.

3. A combination in accordance wtih claim 2 including releasable means for retaining said trigger in a position effecting overriding of said means normally preventing engagement of said driving and driven members.

4. The combination in a chain saw of an engine having a throttle and an output shaft, a trigger connected to said throttle to control the setting thereof, a chain sprocket adapted for driving a saw chain, clutch means for releasably engaging said output shaft and said chain sprocket in driving relationship, means associated with said clutch for normally preventing engagement of said output shaft and said chain sprocket, manually operable means for overriding said means normally preventing engagement of said output shaft and said chain sprocket, and linkage means connecting said throttle controlling trigger and said means normally preventing engagement of said output shaft and said chain sprocket for preventing advancement of said throttle above a predetermined setting when engagement of said output shaft and said chain sprocket is prevented.

5. The combination in a chain saw of an engine having a throttle and an output shaft, a trigger connected to said throttle for controlling the setting thereof, a chain sprocket adapted for driving a saw chain, a clutch releasably connecting said sprocket and said shaft, said clutch including a driving member, a driven member, and means for engaging said driving and driven members in driving relationship, means associated with said means for engaging said driving and driven members and normally peventing engagement of said driving and driven members, manually operable means for overriding said means normally preventing engagement of said driving and drive members, linkage means connecting saidthrottle controlling trigger and said means normally preventing engagement of said driving and driven members for preventing advancement of said throttle above a predetermined setting when engagement of said driving and driven members is prevented.

6. A combination in accordance with claim wherein said throttle controlling trigger is mounted for throttle advancing movement from a predetermined position, and said means connecting said throttle controlling trigger and said means normally preventing engagement of said driving and driven members comprises a member movabe from a position interfering with throttle advancing movement of said throttle controlling trigger in response to overriding of said means normally preventing engagement of said driving and driven members.

7. The combination in a chain saw of a frame, an engine on said frame and including a throttle and an output shaft, a trigger connected to said throttle and mounted on said frame for throttle advancing movement from a predetermined position to control the throttle setting, a handle on said frame, a chain sprocket rotatably mounted on said frame and adapted for driving a saw chain, a clutch releasably connecting said sprocket and said shaft, said clutch including a first drum connected to said shaft and rotatably mounted on said frame, a second drum rotatably mounted on said frame co-axial with said first drum, said first and second drums including aligned cylindrical surfaces, and a helical spring fixed to said second drum and encircling said cylindrical surfaces to provide driving engagement therebetween in response to rotation of said first drum, said helical spring including a radially extending part, a plunger mounted on said frame for movement to a position in the path of rotative movement of said spring part to prevent rotation thereof and driving engagement of said drums, means on said frame biasing said plunger toward said position, a hand grip pivotally mounted on said handle, means connecting said hand grip and said plunger to effect displacement of said plunger from said plunger position in response to pivotal movement of said hand grip, thereby affording engagement of said drums in response to rotation of said first drum, and means mounted on said frame and connected to said hand grip for movement from a position interfering with throttle advancing movement of said throttle controlling trigger in response to displacement of said plunger from said plunger position by operation of said hand grip.

8. The combination in a chain saw of a frame, an engine on said frame and including a throttle and an output shaft, a trigger connected to said throttle and mounted on said frame for throttle advancing movement from a predetermined position to control the throttle setting, a handle on said frame, a chain sprocket rotatably mounted on said frame and adapted for driving a saw chain, a clutch releasably connecting said sprocket and said shaft, said clutch including a first. drum connected to said shaft and rotatably mounted on said frame, a second drum rotatably mounted on said frame co -axial with said first drum, said first and second drums includ ing aligned cylindrical surfaces, and a helical spring fixed to said second drum and encircling said cylindrical surfaces to provide driving engagement therebetween in response to rotation of said first drum, said helical spring including a radially extending part, a plunger mounted on said frame for movement to a position in the path of rotative movement of said spring part to prevent rotation thereof and driving engagement of said drums, means on said frame biasing said plunger toward said position, a hand grip pivotally mounted on said handle for movement between a clutch engaging position and a safety position, means biasing said hand grip toward said safety position, means connecting said hand grip and said plunger to effect displacement of said plunger from said plunger position in response to pivotal movement of said hand grip to said clutch engaging position, thereby affording engagement of said drums in response to rotation of said first drum, and to permit displacement of said plunger to said plunger position in response to release of said hand grip from said clutch engaging position to said safety position, thereby affording disengagement of said drums, and means mounted on said frame for movement to a position interfering with throttle advancing movement of said throttle controlling trigger in response to release of said hand grip from said clutch engaging position to said safety position.

Q. A combination as set forth in claim 8 including centrifugal clutch means connecting said first drum and said output shaft.

10. A chain saw comprising a cutter bar, a saw chain movably supported by said cutter bar, an engine having an output shaft, a trigger connected to said engine to control engine speed, an output member driving said saw chain, a clutch means for releasably engaging said output shaft and said output member in driving relationship, means associated with said clutch for normally preventing engagement of said output shaft and said output member, manually operable means for overriding said means normally preventing engagement of said output shaft and said output member, and means connecting said trigger and said means normally preventing engagement of said output shaft and said output member for preventing engine speed advancement above a predetermined setting when engagement of said output shaft and said output member is prevented.

11. A saw chain comprising a cutter bar, a saw chain movably supported by said cutter bar, means connected to said saw chain for driving said saw chain along said cutter bar, manually operable means selectively engageable with said means for driving said saw chain for mechanically preventing SEUW chain driving operation of said means for driving said saw chain, said manually operable means including a trigger movable to a given position to locate said manually operable means clear of said means for driving said saw chain, and means biasing said trigger away from said given position and to a position located to engage said manually operable means with said means for driving said saw chain to mechanically prevent saw chain driving operation of said means for driving said saw chain, whereby saw chain driving operation is prevented in the absence of the presence of said trigger in said given position.

References Cited UNITED STATES PATENTS 1,838,700! 12/1931 \Meyer 192F096 2,267,996 12/ 1941 Spase et al 192-084 2,610,657 9/1952 ,Kieklaefer 143-32 2,829,748 4/ 195 8 Sacchini 19226 DONALD R. SCHRAN, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,561,165 January 2, 1968 Finn T. Irgens It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 23, for "aid" read and column 4, line 54, beginning with "to prevent" strike out all to and including "mounted" in line 58, same column 4, and insert instead to prevent driving engagement of said drums, means biasing said plunger toward said position, and manually oper able means normally preventing engagement of said driving and driven members and including a trigger pivotally mounted column 5, line 21, for "drive' read driven column 6, line 39, strike out "a".

Signed and sealed this 27th day of May 1969.

(SEAL) 2 Attest:

EDWARD M. FLETCHERJR. Attesting Officer Commissioner of Patents 

1. THE COMBINATION IN A CHAIN SAW OF AN ENGINE HAVING AN OUTPUT SHAFT, A HANDLE CONNECTED TO SAID ENGINE, A CHAIN SPROCKET ADAPTED FOR DRIVING A SAW CHAIN, A CUTTER BAR EXTENDING FROM SAID SPROCKET, A CLUTCH RELEASABLY CONNECTING SAID SPROCKET AND SAID SHAFT, SAID CLUTCH INCLUDING A DRIVING MEMBER, A DRIVEN MEMBER, AND MEANS FOR ENGAGING SAID DRIVING AND DRIVEN MEMBERS IN DRIVING RELATIONSHIP, MEANS ASSOCIATED WITH SAID MEANS FOR ENGAGING SAID DRIVING AND DRIVEN MEMBERS AND NORMALLY PREVENTING ENGAGEMENT OF SAID MEANS FOR ENGAGING SAID DRIVING AND DRIVEN MEMBERS, AND MANUALLY OPERABLE MEANS ON SAID HANDLE FOR OVERRIDING SAID MEANS NORMALLY PREVENTING ENGAGEMENT OF SAID MEANS FOR ENGAGING SAID DRIVING AND DRIVEN MEMBERS. 